Microelectronics fabrication involves the manufacture of integrated circuits which uses dielectric materials as insulating layers between various circuits and layers of circuits. As the device dimensions of advanced microelectronics integrated circuits continue to shrink, the increase in propagation delay, capacitance.coupling between two or more conductive features and power dissipation of the interconnect structure become significant limiting factors.
The capacitance between two or more conductive features is proportional to the dielectric constant, k, of the material which separates the features. These features are usually vias for vertical connections between layers and trenches for horizontal connections within a layer. A dielectric material with a low k value is desirable in reducing the tendency for higher capacitance coupling when conductive features are brought closer together in more advanced circuit designs.
Silicon dioxide which has been typically used as a dielectric material in the microelectronics fabrication industry has a k value of about 4. There is a need for new dielectric materials with a k value below 3. A method of lowering the dielectric constant of silicon oxide is described in U.S. Pat. No. 6,147,009 where a hydrogenated oxidized silicon carbon material (SiCOH) is formed in a chemical vapor deposition (CVD) chamber. Another low k material comprised of carbon doped silicon oxide that is deposited by a CVD method is described in U.S. Pat. No. 6,303,523. To successfully replace silica as a dielectric material, a polymeric material must have a thermal stability to at least 350° C. which is a typical temperature at which dielectric films are cured if they are spin coated on a substrate.
U.S. Pat. No. 6,280,794 discloses a method of forming dielectric material with a low k value by forming pores within a dielectric polymer. The pores contain air with a dielectric constant of 1 which reduces the k value of the two phase film proportional to the volume fraction of air in the polymer film.
U.S. Pat. Nos. 5,874,516 and 5,658,994 disclose poly(arylene ethers) which do not contain any functionalized or reactive groups in the polymer. The utility of these polymers is recited to be for low dielectric insulating layers in integrated circuits and articles containing such poly(arylene ethers).
A trend in the microelectronics fabrication industry is to replace the current conductive material which is aluminum with lower resistivity materials such as copper. Copper or copper ions that diffuse away from the conductive feature can reduce the performance of the device. A dielectric material that has the additional property of being able to trap copper or copper ions and prevent them from diffusing is highly desirable. F. Cotton and G. Wilkinson in “Advanced Inorganic Chemistry” published by Interscience Publishers (1966), page 896 write that cuprous complexes of pπ bonding ligands are known. Aromatic compounds with a lone pair of electrons like pyridine or thiophene are capable of forming π complexes with metals through their p orbitals.